The technology disclosed here relates, inter alia, to a pressure vessel for motor vehicles. The pressure vessel may be, for example, a cryogenic pressure vessel or a high-pressure gas vessel in which fuel is stored.
Pressure vessels expand in a manner dependent on factors such as the internal pressure p or the temperature T of the pressure vessel. For this reason, pressure vessels are attached to the body in accordance with the fixed bearing-floating bearing principle. From the prior art, bearing arrangements with pressure vessel expansion compensation are known, in the case of which the expansions of a pressure vessel in a radial direction R and in the direction of the pressure vessel longitudinal axis A-A are compensated by way of separate mechanisms. Such embodiments are relatively cumbersome and are therefore expensive. Moreover, they require a relatively large amount of structural space. Moreover, they are not capable of transmitting all forces and moments from one end of a pressure vessel to another end of the pressure vessel. For example, the previously known solutions are not capable, in the case of a pressure vessel arranged in the central tunnel of a motor vehicle, of transmitting forces in the direction of travel x in play-free fashion. Furthermore, moments about the vehicle transverse axis y and the vehicle vertical axis z cannot be transmitted in play-free fashion.
It is an object of the technology disclosed here to reduce or eliminate the disadvantages of the previously known solutions. Further objects will emerge from the advantageous effects of the technology disclosed here. The object(s) is/are achieved by way of a pressure vessel for a motor vehicle, having a fastening apparatus designed to connect the pressure vessel to a body of the motor vehicle. The fastening apparatus has: at least two connecting pins and at least two bearings. In each case, one connecting pin is connected to a bearing at a connecting point. The connecting pins and/or the bearings each are connected to the pressure vessel in a pressure vessel attachment region and extend away from the outer surface of the pressure vessel. The pressure vessel attachment regions exhibit in each case an expansion, and the connecting pin and the bearing, in the connecting point, are at least regionally shaped and arranged such that the expansion is kinetically guided with only one translational degree of freedom by way of a movement of the bearing and/or of the connecting pin.
The technology disclosed here relates to a pressure vessel for storing fuel for a motor vehicle. A pressure vessel of this type may be, for example, a cryogenic pressure vessel or a high-pressure gas vessel. The pressure vessel may be used in a motor vehicle which is operated, for example, with compressed natural gas (CNG) or with hydrogen (fuel cell electrical vehicle). The cryogenic pressure vessel may store fuel preferably in the liquid or supercritical state of aggregation. The fuel may be stored in the cryogenic pressure vessel for example at temperatures of approximately 30 K to 360 K. High-pressure gas vessels are preferably designed to store fuel permanently at a pressure of over approximately 350 bar(g), more preferably of over approximately 500 bar(g), and particularly preferably of over approximately 700 bar(g).
The pressure vessel includes a fastening apparatus, wherein the fastening apparatus is designed to connect the pressure vessel, at one side of the pressure vessel, to a body of the motor vehicle. Here, a part of the body is to be understood to mean any suitable structure of the motor vehicle to which the pressure vessel can be fastened. For example, the at least one pressure vessel of the motor vehicle may be arranged in the central tunnel. Furthermore, however, the pressure vessel may also be accommodated elsewhere, for example under the rear seats.
The fastening apparatus may have, on one side or on one end of the pressure vessel, at least two connecting pins which may each be connected, in particular rigidly, to the pressure vessel in a pressure vessel attachment region. The at least two connecting pins may extend away from the outer surface of the pressure vessel. The connecting pin may also be referred to as a connecting rod or connecting bolt. The connecting pin is preferably formed so as to be rigid or immovable relative to the pressure vessel or relative to the body.
The at least two connecting pins may each be guided or received in a bearing. The bearings or guides are particularly preferably suitable for permitting a relative displacement between the connecting pins and the bearings or guides. Furthermore, the bearings may preferably be fixing mechanisms such as are likewise disclosed here.
In each case one connecting pin may be connected to a bearing at a connecting point V.
Furthermore, as an alternative to the preceding refinement, the fastening apparatus may also, on one side or on one end of the pressure vessel, have at least two bearings which are each connected to the pressure vessel in a pressure vessel attachment region and which extend away from the outer surface of the pressure vessel. This aspect constitutes the kinematic reversal of the preceding aspect. Instead of the one or more bearings being arranged on the body, it is also possible for the one or more bearings to be arranged on the pressure vessel. The at least two connecting pins would then be arranged on, and connected to, the body. It is also possible for a combination (one bearing and one connecting pin) to be connected to the pressure vessel.
In the pressure vessel attachment regions, the pressure vessel may exhibit in each case an expansion E and/or expand in said direction E.
The connecting pin and the bearing can, in the connecting point V, be at least regionally shaped and arranged such that the expansion E is kinematically guided with only one translational degree of freedom by way of a movement of the bearing and/or of the connecting pin. The expansion E in the pressure vessel attachment region B is preferably thereby at least partially compensated. In other words, the expansion E causes a movement of the component (bearing or connecting pin) that is rigidly connected thereto. The component is, however, of such a form that it can follow the movement of the expansion E such that, as a result of the expansion E itself, no additional forces and/or moments, or only small additional forces and/or moments, are transmitted at the connecting point V to the further component of the fastening apparatus (corresponding connecting pin or bearing).
A movement of the bearing and/or of the connecting pin with only one translational degree of freedom means that, during the translational movement in space, the coordinates x, y and z of the movement are dependent on one another and cannot be varied independently of one another. The only one translational degree of freedom may be a movement along a straight or curved path. The exact profile of the path arises from the vessel geometry, the expansion behavior thereof and the arrangement of the bearings/connecting pins.
In the case of the technology disclosed here, all other degrees of freedom are restricted. In this way, it is possible for a greater number of force and/or moment components to be transmitted in play-free fashion along the vehicle axes than in the case of previously known solutions. Furthermore, such a suspension arrangement or fastening apparatus for a pressure vessel is easy to realize. It is preferable for four connecting pins to be provided on each side of the pressure vessel.
A special case is a linear or straight expansion E of the pressure vessel attachment region B. In the special case of a linear expansion E, wherein the angle α thus remains constant for all expansion states, the connecting pins are at least regionally straight, and the then constant expansion direction E may preferably be at least regionally collinear with respect to the longitudinal axis of the connecting pins and/or of the bearings. By virtue of the fact that the expansion E, that is to say the expansion caused, for example, by the change in pressure vessel internal pressure or temperature, is parallel to the longitudinal axis of the connecting pins, only a linear movement takes place at the connecting point V at each suspension point. It is thus possible for components of particularly simple construction to be used.
The expansion E may run collinearly, or with a slight offset, with respect to the axes of the connecting pins and/or of the bearings. If the longitudinal axes of the connecting pins and/or of the bearings are arranged offset with respect to the expansion E, for example with an offset toward the outside, it may be possible by way of such a structure for any moments to be transmitted in a more effective manner. For the most part, the special case of the parallel arrangement of the expansion E and the longitudinal axes of the bearings/connecting pins will be discussed below. The disclosed technology is, however, likewise applicable to translational movements with only one degree of freedom along curved paths.
The at least two connecting pins and/or the at least two bearings may be arranged so as to be angled with respect to one another. If the connecting pins and/or the at least two bearings are arranged so as to be angled with respect to one another—that is to say not parallel with respect to one another—it is possible for further forces and moments to be transmitted. If the connecting pins and/or the bearings were arranged parallel, it would not be possible for forces to be transmitted in play-free fashion in the direction of the collinear axis (for example of the pressure vessel longitudinal axis).
The longitudinal axes of the at least two connecting pins and/or of the at least two bearings may be arranged at an angle β with respect to one another, which angle lies between 2° and 178°, preferably between 5° and 90°, and particularly preferably between 10° and 50°. Depending on the design of the pressure vessel, the expansion E resulting from the pressure vessel loading may lie in these angle ranges. The resulting expansion E can be predicted in an effective manner in advance by way of simulations and tests.
The longitudinal axes of the at least two fastening pins and/or of the at least two bearings are preferably arranged so as to be angled, that is to say not parallel, with respect to the pressure vessel longitudinal axis A-A. A degree of freedom along the pressure vessel longitudinal axis A-A is then eliminated. The longitudinal axes of the at least two fastening pins and/or of the at least two bearings may be arranged at an angle α with respect to the longitudinal axis A-A of the pressure vessel, which angle lies between 2° and 178°, preferably between 5° and 90° and particularly preferably between 10° and 50°. If the pressure vessel is installed, for example, in the central tunnel, it is thus possible for forces to be transmitted in the vehicle longitudinal direction. This task is performed, in vehicle architectures that are common nowadays, by longitudinal members. If the tank now partially performs this task, it is possible for vehicle mass to be reduced, and/or for vehicle stiffness to be increased.
The bearings may be in the form of ball joints, in particular in the form of ball joints in which the connecting pins are received in displaceable fashion and which furthermore permit a rotation of the respective connecting pins, similarly to the situation, for example, in the case of ball joints in upper links of tractors. It is thus possible for the bearing arrangement formed from a bearing and a connecting pin to have not only one translational degree of freedom but likewise at least one, preferably multiple, rotational degree(s) of freedom.
The fastening apparatus disclosed here may be provided on each side of the pressure vessel. The fastening apparatus may preferably have four connecting pins and four bearings, which are expediently arranged concentrically around the boss. The boss itself is thus easily accessible for any supply lines.
There is a demand to further improve, or actively change, the stiffness of the body by way of the pressure vessel structure.
This is achieved, inter alia, by way of a pressure vessel for a motor vehicle, having a fastening apparatus, the fastening apparatus being designed to connect the pressure vessel to the body of the motor vehicle. Here, the fastening apparatus may have at least one connecting pin which is displaceable relative to the body or relative to the pressure vessel. The connecting pin may, for example, be connected, preferably rigidly, to the pressure vessel or to the body. In particular, the connecting pin may be one of the at least two connecting pins discussed above.
The technology disclosed here furthermore includes at least one fixing mechanism which may be connected to the body or to the pressure vessel (that is to say inversely with respect to the connecting pin; that is to say if the fixing mechanism is connected to the body, the connecting pin is connected to the pressure vessel, and vice versa). The fixing mechanism may be designed to at least temporarily fixedly clamp the connecting pin.
The fixing mechanism is preferably rigidly or immovably connected to the body or to the pressure vessel. The fixing mechanism may be designed to at least temporarily fixedly clamp the connecting pin when a controller transmits a corresponding control signal. If the remaining degree of freedom in the direction of the longitudinal axis of the connecting pin or of the bearing is likewise blocked, the body is additionally stiffened. At the same time, by way of this regulable fixing mechanism, it is possible for any expansions, such as may arise, for example, as a result of pressure changes or temperature changes in the pressure vessel, to be compensated.
It is particularly preferable for the connecting pin to be guided in the fixing mechanism. The fixing mechanism is preferably simultaneously the guide or bearing arrangement for the connecting pin. In other words, the fixing mechanism may preferably form the bearing discussed above. The fixing mechanism is preferably arranged parallel to the connecting pin. It is preferable for at least two, particularly preferably four fixing mechanisms or bearings or guides to be provided on each side of the pressure vessel.
The fixing mechanism may be designed to fixedly clamp the connecting pin when the motor vehicle is subject to a dynamics demand above a first threshold value. It is thus possible, for example, for the motor vehicle to be additionally stiffened in the presence of a high dynamics demand. An increased dynamics demand may result, for example, from the road condition and the driving style of the vehicle driver.
The dynamics demand may be determined for example from the measurement values of a dynamic stability control (DSC) system. For this purpose, use may be made of sensors (rate of rotation sensors, transverse acceleration sensors, etc.) that are already installed in any case.
The fixing mechanism may be designed to not fixedly clamp the connecting pin when the motor vehicle is subject to a dynamics demand below a first threshold value, for example when the motor vehicle is at rest. If the connecting pin is not fixedly clamped in this state, it is possible for any internal stresses induced by a change of internal pressure or temperature of the pressure vessel to be dissipated again. This may take place in the state of rest without an additional displacement actuator. Moreover, unknown dynamic influences distort the adjustment.
The fixing mechanism may be designed to not fixedly clamp the connecting pin when the pressure vessel is being refilled. When the motor vehicle undergoes tank refilling, the expansion of the vessel changes considerably. If the fixing mechanism were to fixedly clamp the connecting pin, it would be possible for undesired, possibly even damaging loads to be transmitted to the body.
The fixing mechanism is particularly preferably fixed by at least one piezo element. In particular, the at least one piezo element and the fixing mechanism may be designed such that the fixing mechanism prevents the displacement of the connecting pin if no electrical voltage is applied to the piezo element. Such elements can prevent the displacement of the connecting pin in a particularly rapid, inexpensive and precise manner.
The fixing mechanism may be in the form of an electromechanical actuator. In addition to a refinement in which the fixing mechanism merely prevents the displacement, it is also possible for an actuator to be provided which actively adjusts or displaces the connecting pin. It is thus possible for the internal stress or the stiffness of the body to be actively influenced. Depending on the driving mode preselected by the vehicle driver, the body is then made stiffer or softer. It is preferably possible for the electromechanical actuator to be driven by at least one piezo element.
In a particularly preferred refinement, the electromechanical actuator is an inchworm motor. An inchworm motor is a piezoelectric actuator which, in its interior, can move or actuate a shank, in this case the fastening pin, with nanometer precision. For this purpose, the inchworm motor has two gripping regions which are spaced apart from one another in an axial direction by piezo elements and which can firmly grip the fastening pin in alternating fashion and with a short time overlap. After gripping, the piezo elements change their length, whereby the fastening pin is displaced. With such an inchworm motor, it is possible even in the presence of high forces for the connecting pin to be actuated in a highly precise fashion and with continuous traction. Furthermore, the mechanical stress can be measured simultaneously. This thus constitutes an active strut which can positively influence the vehicle characteristics. A further advantage of the inchworm motor is that the traction can be realized at all times.
The technology disclosed here also relates to a motor vehicle having a pressure vessel presented here and having at least one controller. The controller may be designed to release the at least one connecting pin if an operating parameter of the fixing mechanism lies above an operating parameter threshold value. For example, the operating parameter may be the voltage of the actuator (for example piezo element, inchworm motor). This voltage may be representative of the mechanical load to which the pressure tank or the suspension arrangement of the pressure tank is subjected. Depending on the mechanical load, it can then thus be decided by the controller whether the at least one connecting pin is released or fixedly clamped. Such a regulation system can be realized in particularly simple and precise form.
The controller may furthermore be designed to release the at least one connecting pin if a collision is identified. A collision may be identified for example on the basis of further detection systems of the vehicle. Such detection systems are known and are used in conjunction with airbags, for example. If the at least one connecting pin is not fixedly clamped by the fixing mechanism during a collision, it is subject to less mechanical load during the collision event. The amount of damage to the pressure vessel can thus be at least reduced.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.